Barrier Contraceptives

Spermicides:

Vaginal foams, creams, and suppositories contain agents that provide a chemical barrier to sperm by damaging sperm cell membranes and thus preventing fertilization. Most spermicides contain nonoxynol-9 and are available without a prescription. These products are similar in efficacy; the pregnancy rate is 19% with perfect use and 28% with typical (ie, inconsistent) use.

Spermicides should be placed in the vagina at least 10 to 30 min before sexual intercourse and reapplied before each coital act. Because their efficacy is limited, spermicides are often used with other barrier methods. Spermicides do not reliably protect against sexually transmitted diseases (STDs). Also, spermicidal agents may cause vaginal irritation that increases the risk of HIV transmission. For this reason, condoms are no longer lubricated with nonoxynol-9.

Condoms:

Condom use reliably reduces the risk of STDs, including HIV infection. Condoms may be made of latex, polyurethane, silicone rubber, and lamb intestine. Lamb-intestine condoms are impenetrable to sperm but not to many of the viruses that can cause serious infections (eg, HIV). Thus, latex and polyurethane condoms are preferred. Condoms also protect against human papilloma virus (HPV), thus reducing the risk of precancerous cervical lesions.

The male condom is the only reversible male contraceptive method other than withdrawal, which has higher contraceptive failure rates.

The male condom is applied before penetration; the tip is pinched shut and should extend about 1 cm beyond the penis to collect the ejaculate.

The female condom is a pouch with an inner and an outer ring; the inner ring is inserted into the vagina, and the outer ring remains outside and covers the perineum. The female condom should be placed no more than 8 h before intercourse and should be left in the vagina for 6 h after intercourse. The penis should be carefully guided through the external ring to make sure that the ejaculate is collected in the pouch.

When the penis is removed after intercourse, care must be taken to avoid spilling condom contents. Emergency contraception should be used if contents spill, the condom slips, or the condom breaks. A new condom should be used for each coital act.

Pregnancy rates at 1 yr are 2% with perfect use and 18% with typical use for the male condom and 5% with perfect use and 21% with typical use for the female condom.

Diaphragm:

The diaphragm is a dome-shaped rubber cup with a flexible rim that fits over the cervix and upper part and lateral wall of the vagina. Diaphragms are made in various sizes. They are usually used with a spermicide and, together, provide an effective barrier to sperm. Spermicide is applied to the diaphragm before insertion. After the first coital act, additional spermicide should be inserted into the vagina before each subsequent act. Diaphragms can be washed and reused.

A health care practitioner fits a diaphragm for a woman so that it is comfortable for her and her partner. After childbirth or a significant weight change, the woman needs to be refitted. The diaphragm should remain in place for at least 6 to 8 h but not more than 24 h after intercourse. Pregnancy rates in the first year are about 6% with perfect use but about 12% with typical use.

Diaphragms were once widely used (one third of women in 1940), but by 2002, only 0.2% of women in the US reportedly used them. This decline in use is largely due to the development of many other more effective contraceptive methods. Also, the need for a physician visit for fitting and adverse effects (eg. discomfort, vaginal irritation) may have contributed to the decline.

A new diaphragm is being developed. This diaphragm is considered to be one size fits most. It is made of silicone and reportedly softer and more durable than traditional latex diaphragms. This diaphragm may be useful in developing nations where access to medical care is limited.

Cervical cap:

The cervical cap resembles the diaphragm but is smaller and more rigid. It must be inserted before intercourse; it should remain in place for at least 6 h after intercourse and not more than 48 h. Pregnancy rates are 8% with typical use in the first year; rates are higher among parous women because obtaining a secure fit after childbirth is difficult.

Only one cervical cap is available in the US. It comes in 3 sizes (small, medium, large); size is chosen based on a woman's pregnancy history. A health care practitioner must write a prescription before the cervical cap can be used, but it does not require a custom fitting.

Contraceptive sponge:

The contraceptive sponge acts as both a barrier device and a spermicidal agent. It can be purchased without a prescription and can be inserted up to 24 h before intercourse. It should be left in place for at least 6 h after intercourse. Maximum wear time should not exceed 30 h. Pregnancy rates with typical use are 12% for nulliparous women and 24% for parous women.